Caroline Wozniacki leads the head-to-head against Sara Errani 3-1, including their sole clay meeting - all the way back in 2007, in the quarterfinals of the ITF $50,000 event in Latina, Italy, 6-1, 6-3. Errani's only win came the following year, 6-4, 6-4 in the Portoroz semifinals. The pair have not played since the 2014 US Open quarterfinals, which Wozniacki took 6-0, 6-1.
Maria Sakkari is yet to lose a set to Aleksandra Krunic in two meetings - both of which took place in Miami, in 2016 and last month, and finished with almost identical scorelines: 7-6(3), 6-1 and 7-5, 6-1.
Qualifier Danka Kovinic, the 2016 runner-up here, is seeking to make her first WTA quarterfinal since October 2016, when she reached the Tianjin semifinals. The Montenegrin has won her only previous meeting against Arantxa Rus, 4-6, 6-3, 6-4 in the qualifying of Florianopolis in 2014.
Donna Vekic is going for her maiden WTA quarterfinal on clay. The Croat has only won consecutive main draw matches on clay once before, at Roland Garros 2015; she leads the head-to-head 1-0 over Ajla Tomljanovic, whom she defeated 6-7(4), 6-2, 6-4 in the qualifying of Wuhan in 2014.
A win over Caroline Wozniacki would mean a fourth career Top 5 win for Sara Errani, and the first since the Italian beat Petra Kvitova in the first round of Beijing in 2014; it would also match Errani's career-best win by ranking, over Li Na in the 2014 Rome quarterfinals.
CENTER (starts 12.30pm)
Aleksandra KRUNIC (SRB) vs Maria SAKKARI (GRE)
Polona HERCOG (SLO) vs Kateryna BONDARENKO (UKR)
 Caroline WOZNIACKI (DEN) vs Sara ERRANI (ITA)
Donna VEKIC (CRO) vs Ajla TOMLJANOVIC (AUS)
COURT 1 (starts 11am)
[Q] Danka KOVINIC (MNE) vs [Q] Arantxa RUS (NED)
 Xenia KNOLL (SUI) / Anna SMITH (GBR) vs Raluca OLARU (ROU) / Yana SIZIKOVA (RUS)
LIANG Chen (CHN) / ZHANG Shuai (CHN) vs [WC] Ayla AKSU (TUR) / Harriet DART (GBR)
[PR] Oksana KALASHNIKOVA (GEO) / Galina VOSKOBOEVA (KAZ) vs Natela DZALAMIDZE (RUS) / Anna KALINSKAYA (RUS)
 Kateryna BONDARENKO (UKR) / Aleksandra KRUNIC (SRB) vs Maria IRIGOYEN (ARG) / Ellen PEREZ (AUS)